Alan M. Turing (1912 - 1954)

Alan Mathison Turing was born on June 23rd 1912 in Paddington, London. He was
educated at Sherborne School, and then went to King's College, Cambridge in
1931 to read Mathematics.

Alan Turing was a brilliant original thinker. Formally a mathematician,
in his lifetime he studied and wrote papers over a whole spectrum of
subjects, from philosophy and psychology through to physics, chemistry
and biology. He was probably at his happiest when he could combine
high-level thinking with hands-on experience with machinery or experiments.

In addition to his many other interests, for most of his postgraduate life he
probably had a deeper understanding of computers and their potential in the
future than anyone else.

For the full story of Turing's life, visit the
Turing Web Site, from which
much of this description is derived.

Turing graduated from Cambridge in Mathematics in 1934, and was a fellow
at Kings for two years, during which he wrote his now famous paper published
in 1937 "On Computable Numbers with an application to the
Entscheidungsproblem", which postulated the Turing Machine. The
Entscheidungsproblem was the mathematical problem of Decidability. (He had been
made aware of the problem from a lecture course by
Max Newman, and it was to
Newman he first showed the paper.)

A Turing Machine was a specific mechanical device that could carry out
some specific task in a systematic way. Each Turing Machine would work in a
similar manner, using mechanisms related to the computer concepts of input,
output and a program. The Universal Turing Machine was essentially a
similar device, the specific task of which was to read in a description of any
Turing machine in a standard format and then execute any task it was designed
to undertake. The Universal Turing Machine would therefore
carry out any systematic process man could devise.

The Turing Machine was a somewhat obscure device; there was no intention of
building one; it was essentially an abstract concept in a paper considering
logic and philosophy. However, relative to the high levels of theory in
which he was operating, it was a concrete, buildable machine. It had
little similarity to the classic 'von Neumann computer' of 1945, and was not
well understood. However the paper anticipated many computer-related concepts,
like input, output, memory, coded programs, algorithms, compilers/interpreters,
and the finite-state machine.

Turing went to the Institute of Advanced Studies at Princeton, the mecca for
logicians, in September 1936 for two years and studied for a
Ph.D. under Alonzo Church. Here he met von Neumann,
who was like Turing also a brilliant mathematician who at that time only had a
secondary interest in practical computers. Von Neumann in fact offered Turing a
post in 1938, which would have enabled him to stay in the U.S. However Turing
decided to return to his fellowship at Cambridge. He was already showing
his practical interest in making computing devices, bringing home from the
States a small electronic multiplier he had made as part of an enciphering
machine, and in Cambridge starting to build an analogue mechanical device to
test the Riemann hypothesis. Soon after his return, in August 1938, he was
contacted by the Government Code and Cypher School to act as
a consultant in their efforts to break the German Enigma codes.

The day after the war broke out Turing "joined up" full time at
the Government Code and Cypher School, which had just moved to Bletchley Park.
He was in the first handful of the stream of able mathematicians
drafted into their code-breaking operations. In the next three years Turing was
the key figure in the continual battle to decode messages encrypted by the
increasingly complex Enigma machines, using the 'Bombe' machine. In particular
he took charge of the most difficult code-breaking task, the breaking of the
German naval codes. The Bombe was an
electro-mechanical device, developed by
Turing with help from another mathematician W. G. Welchman, inspired by the
Polish 'Bomba'. The periods when the Naval code could be broken saw dramatic
reductions in the shipping losses from the Atlantic convoys so essential to
the conduct of the Allied war effort.

In November 1942 Turing went to the
States for four months, to liaise at the highest level on the current U-boat
crisis and on a proposed scrambling device they were building to maintain
secrecy
in conversations between Churchill and Roosevelt. At this time all other Enigma
signals but the German Navy's were being routinely decoded, but the Navy had
increased their complexity in February 1942, and the ability to decode their
signals had then been lost and had not yet been restored. By the time Turing
returned to the U.K., the ability to decode had been restored, under his
deputy, and his deputy remained in charge. Turing moved on to a general
consultancy role, and to work on a Speech Secrecy system. The American system
comprised three roomfuls of equipment (one each for the White House,
Pentagon and Whitehall), and Turing thought up a much smaller electro-mechanical
device, about the size of a typewriter, which would obviously make the facility
more widely available!

Turing was therefore not actively involved in the
Colossus project (1943-45)
directed by Max Newman, to decode the second
generation of German coded communications, which were based on Lorenz machines.
These used a completely different mechanism and methodology from the Enigma
machines, and correspondingly their codes were broken using a completely
different mechanism and methodology. Note however that the decoding procedures
for both the Enigma and Lorenz involved imaginative, elaborate and sophisticated
theories and processes, and the mechanical device used to provide the initial
breakthrough for a new code (i.e. the Bombe and the Colossus respectively) was
only one part of a complex operation. Turing made major theoretical
contributions to the solution of both the Enigma and Lorenz codes; but whereas
he made the key contribution to the design of the Bombe, which was a highly
specific
electro-mechanical device that bore little relation to a computer, ironically
he was little involved in the design of Colossus, which was in effect a special
purpose electronic digital computer.

Although Turing was not directly involved in the Colossus project, he knew what
was going on. He saw the
potential of the electronic computer to realise his long-standing dream of a
machine that could carry out processes previously assumed achievable only by
the human brain. He well understood that to turn it into a Universal Computer
it needed the addition of a large electronic store which could store
instruction codes as well as numbers. So in the last year or two of the war he
learnt all he could about electronics, partly in connection
with his Speech Secrecy project, and was rewarded
when at the end of the war he was invited by the National Physical
Laboratory to design a computer. This he did by early 1946, designing the ACE
around the only viable storage device perceived at the time, the
Mercury Acoustic Delay Line. However,
there were
delays in starting to build his design, and Turing, disillusioned,
was allowed to return to Cambridge for a "sabbatical" year (1947/48), returning
to theoretical work and studying neurology and physiology. During the period
that progress was stalled, Turing spent a lot of time on coding prospective
routines, thinking about programming in general, and thinking about how the
computer could be used to illuminate the mechanisms of the human mind. On being
offered a job by Max Newman, now a Professor in the Department of Mathematics at
the University of Manchester, he resigned from NPL and came to Manchester in
September 1948.

Turing joined the Department of Mathematics as a Reader, with
the nominal title of "Deputy Director of the Royal Society Computing Machine
Laboratory". (The Royal Society Computing Machine Laboratory was the room
the Baby occupied; there was no known "Director"!) It is not clear what his
official duties were initially with respect to the Baby/Mark 1 project.
Before Turing started work in Manchester he asked for the Baby order
code and sent up a routine for long division, which was corrected and got
working by Tootill. As soon as the
Manchester Mark 1 was generally available for
use in April 1949, he enthusiastically set about using it, especially to
investigate Mersenne Primes, in
collaboration with Newman. In the summer of
1949 he was instrumental in acquiring paper tape equipment and assisted
Dai Edwards in attaching it to the
Mark 1. Meanwhile, he was continuing his theoretical work and in 1950
published another famous paper "Computing Machinery and Intelligence", which
anticipated the subject of Artificial Intelligence.

Turing made contributions to the extra orders added in the Ferranti Mark 1,
notably the random number generator. It is also likely that he and Newman
influenced the comprehensive set of instructions provided on the Manchester
Mark 1 in connection with the double length accumulator, since they required
multi-length arithmetic for their Mersenne Primes work. (In practice
there was little subsequent usage of the Mark 1s for anything longer than
double-length arithmetic).

However, the main formal contribution Turing made
to the Mark 1
project was that he worked on providing the early software requirements for
the Manchester Mark 1, with the full time help of
Cicely Popplewell, and wrote
the first
programming manual for the
Ferranti Mark 1.
So it was Alan Turing who was mainly responsible for the decision to use the
Base-32 Numerical System and he devised with Cicely
the Scheme A method of program organisation.
He would therefore have been involved in writing the Scheme A Input routines
and standard subroutines for general use.

By 1951, Newman and Turing (and indeed Freddie Williams) had withdrawn
from active involvement in the Mark 1 Project and subsequent computer
development, leaving the newly-arrived Tony
Brooker to look after the interests of the programmer.

However Turing was still a keen user of the computer as a tool for his research
interests, which now turned to "morphogenesis", the theory of growth and form
in biology. And he was was always ready informally to help out other
programmers of the Mark 1 with their problems.

Turing's life came to a sad and untimely end in June 1954, from cyanide
poisoning, with a verdict returned of suicide, though he did legitimately have
cyanide in the house in connection with chemical experiments. It is difficult
not to believe that this was precipitated by his trial in March 1952 on charges
of homosexuality. As ever Turing was decades ahead of his time and was
relatively open
about his sexuality. But at that time a homosexual relationship was a crime
and a scandal. Turing agreed to take
hormone therapy for a year instead of going to prison. However it now became
clear that he was a major security risk, both with respect to his work at
Bletchley Park and his association with US security from his 1942/43 visit
(remember the McCarthy era was now in full flow). He may well have thought that
this would hound him for the rest of his life.